Methods and apparatus for package with interposers

ABSTRACT

An interposer may comprise a metal layer above a substrate. A dam or a plurality of dams may be formed above the metal layer. A dam surrounds an area of a size larger than a size of a die which may be connected to a contact pad above the metal layer within the area. A dam may comprise a conductive material, or a non-conductive material, or both. An underfill may be formed under the die, above the metal layer, and contained within the area surrounded by the dam, so that no underfill may overflow outside the area surrounded by the dam. Additional package may be placed above the die connected to the interposer to form a package-on-package structure.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.13/706,593 entitled “Methods and Apparatus for Package withInterposers,” filed on Dec. 6, 2012, which application is herebyincorporated by reference herein.

BACKGROUND

Since the invention of the integrated circuit (IC), the semiconductorindustry has experienced rapid growth due to continuous improvements inthe integration density of various electronic components (i.e.,transistors, diodes, resistors, capacitors, etc.). For the most part,this improvement in integration density has come from repeatedreductions in minimum feature size, which allows more components to beintegrated into a given area. These smaller electronic components alsorequire smaller packages that utilize less area than previous packages.Some smaller types of packages for semiconductor devices include quadflat pack (QFP), pin grid array (PGA), ball grid array (BGA), flip chips(FC), three dimensional integrated circuits (3DICs), wafer levelpackages (WLPs), and package on package (PoP) devices.

A 3DIC may be formed by stacking two IC dies on top of each other toachieve a smaller size package. One type of 3DIC is thepackage-on-package (PoP) structure, wherein multiple dies coupled torespective substrates can be stacked on top of each other. A first dieis electrically coupled to a first substrate to form a first circuit.The first circuit includes first connection points for connecting to asecond circuit. The second circuit includes a second die and a secondsubstrate having connection points on each side of the substrate. Thefirst circuit is stacked and electrically coupled on top of the secondcircuit to form the PoP structure. The PoP structure can then beelectrically coupled to a PCB or the like using electrical connections.

Another type of 3DIC is formed using a silicon interposer substrate(either passive or active) to provide much finer die-to-dieinterconnections, thereby increasing performance and reducing powerconsumption. In these situations, power and signal lines may be passedthrough the interposer by way of through vias (TVs) in the interposer.For example, two dies are bonded on top of each other with the lower diebeing coupled to the interposer using contact pads located on theinterposer. The contact pads can then be electrically coupled to aprinted circuit board (PCB) or the like using electrical connections.

In a 3DIC package, an underfill material may be used between a die and asubstrate or an interposer to strengthen the attachment of the die tothe substrate or the interposer to help to prevent the thermal stressesfrom breaking the connections between the die and substrate orinterposer. However, the underfill material may overflow or bleed toconnectors such as BGA balls, causing warp on the interposer anddisrupting electrical connections. Methods and apparatus are needed toprevent underfill materials to overflow or bleed on BGA balls whileforming semiconductor packages.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIGS. 1(a)-1(c) illustrate cross-sectional views of an embodiment of aninterposer with a dam and a package formed with the interposer;

FIGS. 2(a)-2(c) illustrate top views of embodiments of a package formedon an interposer with a dam or multiple dams; and

FIG. 3 illustrates an embodiment of a package on package, where apackage is formed on an interposer with a dam.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the embodiments andare not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the embodiments of the present disclosure arediscussed in detail below. It should be appreciated, however, that thepresent disclosure provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the disclosure, and do not limit the scope of the disclosure.

As will be illustrated in the following, methods and apparatus for aninterposer with a dam, which may be used in packaging dies, aredisclosed. An interposer may comprise a metal layer on a substrate. Adam or a plurality of dams may be formed on the metal layer. A damsurrounds an area of a size larger than a size of a die which may beconnected to a contact pad on the metal layer within the area. A dam maycomprises a metal material, or a non-conductive material. An underfillmay be formed under the die, above the metal layer, and contained withinthe area surrounded by the dam, so that no underfill may overflowoutside the area surrounded by the dam.

FIG. 1(a) illustrates a cross-sectional view of an interposer 100. Theinterposer 100 comprises a substrate 101. A plurality of through vias(TVs) 103 may be formed through the substrate 101. A plurality ofdevices 105, either active or passive, may be formed within thesubstrate 101 as well. A first metal layer 115 may be formed on a firstside of the substrate 101. First contact pads 117 may be formed on thefirst metal layer 115. A second metal layer 119 and second contact pads121 may be formed over a second side of the substrate 101. While layers115 and 119 are shown schematically as a single continuous layer, oneskilled in the art will recognize that this represents variousinterconnects formed as distinct features within a common layer. A dam113 may be formed on the first metal layer 115, surrounding an area 112.A contact pad may be located within the area 112 and another contact padmay be located outside the area 112, which are not shown. There may beother layers such as a passivation layer, or a polymer layer formedbelow the first metal layer 115, which are not shown. Each of thesestructures is discussed in greater detail in the following paragraphs.

As illustrated in FIG. 1(a), the substrate 101 for the interposer 100may be, e.g., a silicon substrate, doped or undoped, or an active layerof a silicon-on-insulator (SOI) substrate, used to provide support forthe interposer 100. However, the substrate 101 may alternatively be aglass substrate, a ceramic substrate, a polymer substrate, or any othersubstrate that may provide a suitable protection and/or interconnectionfunctionality. These and any other suitable materials may alternativelybe used for the substrate 101.

A plurality of devices 105 may be formed within the substrate 101. Asone of ordinary skill in the art will recognize, a wide variety ofactive devices and passive devices such as transistors, capacitors,resistors, inductors and the like may be used to generate the desiredstructural and functional requirements of the design for the interposer100. The devices 105 may be formed using any suitable methods eitherwithin or else on the surface of the substrate 101.

However, as one of ordinary skill will recognize, the above describedsubstrate 101 with devices 105 is not the only substrate that may beused. Alternative substrates, such as a package substrate or aninterposer that does not have devices therein, may alternatively beutilized. These substrates and any other suitable substrates mayalternatively be used and are fully intended to be included within thescope of the present embodiments.

Additional metallization layers may be formed over the substrate 101 andthe devices 105 to connect the various devices to form functionalcircuitry. Contact pads may be formed over and in electrical contactwith the metallization layers. Furthermore, passivation layers may beformed on the substrate 101 over the metallization layers and thecontact pads. Additional polymer layer may be formed on the passivationlayer. All those metallization layers, contacts, passivation layers, andpolymer layers are not shown in FIG. 1(a).

A plurality of TVs 103 may be formed through the substrate 101. The TVs103 may be formed by applying and developing a suitable photoresist, andthen etching the substrate 101 to generate TV openings. The openings forthe TVs 103 at this stage may be formed so as to extend into thesubstrate 101 to a depth at least greater than the eventual desiredheight of the finished interposer 100. Accordingly, while the depth isdependent upon the overall design of the interposer 100, the depth maybe between about 1 μm and about 700 μm below the surface on thesubstrate 101, with a preferred depth of about 50 μm. The openings forthe TVs 103 may be formed to have a diameter of between about 1 μm andabout 100 μm, such as about 6 μm.

Once the openings for the TVs 103 have been formed, the openings for theTVs 103 may be filled with, e.g., a barrier layer and a conductivematerial. The barrier layer may comprise a conductive material such astitanium nitride, although other materials, such as tantalum nitride,titanium, or the like may alternatively be utilized. The barrier layermay be formed using a chemical vapor deposition (CVD) process, such asplasma enhanced CVD (PECVD). However, other alternative processes mayalternatively be used. The barrier layer may be formed so as to contourto the underlying shape of the opening for the TVs 103.

The conductive material for the TVs 103 may comprise copper, althoughother suitable materials such as aluminum, alloys, combinations thereof,and the like, may alternatively be utilized. The conductive material maybe formed by depositing a seed layer and then electroplating copper ontothe seed layer, filling and overfilling the openings for the TVs 103.Once the openings for the TVs 103 have been filled, excess barrier layerand excess conductive material outside of the openings for the TVs 103may be removed through a grinding process such as chemical mechanicalpolishing (CMP), although any suitable removal process may be used.

Once the conductive material is within the openings for the TVs 103, athinning of the second side of the substrate 101 may be performed inorder to expose the openings for the TVs 103 and to form the TVs 103from the conductive material that extends through the substrate 101. Inan embodiment, the thinning of the second side of the substrate 101 mayleave the TVs 103 intact. The thinning of the second side of thesubstrate 101 may be performed by a planarization process such as CMP oretching.

However, as one of ordinary skill in the art will recognize, the abovedescribed process for forming the TVs 103 is merely one method offorming the TVs 103, and other methods are also fully intended to beincluded within the scope of the embodiments.

Alternatively, the TVs 103 may be formed to extend through layers of theinterposer 100 located over the substrate 101 such as the first metallayer 115 (described further below). For example, the TVs 103 may beformed either after the formation of the first metal layer 115 or elseeven partially concurrently with the first metal layer 115. For example,the openings for the TVs 103 may be formed in a single process stepthrough both the first metal layer 115 and the substrate 101.Alternatively, a portion of the openings for the TVs 103 may be formedand filled within the substrate 101 prior to the formation of the firstmetal layer 115, and subsequent layers of the openings for the TVs 103may be formed and filled as each of the first metal layer 115 areindividually formed. Any of these processes, and any other suitableprocess by which the TVs 103 may be formed, are fully intended to beincluded within the scope of the embodiments.

The first metal layer 115 may be formed over the first side of thesubstrate 101 to interconnect the first side of the substrate 101 toexternal devices on the second side of the substrate 101. The firstmetal layer 115 may be a redistribution layer (RDL). While illustratedin FIG. 1(a) as a single layer of interconnects, the first metal layer115 may be formed of alternating layers of conductive material and maybe formed through any suitable process (such as deposition, damascene,dual damascene, etc.). In an embodiment there may be one or more layersof metallization, but the precise number of layers within the firstmetal layer 115 is dependent at least in part upon the design of theinterposer 100.

The first contact pads 117 may be formed over and in electrical contactwith the first metal layer 115. The first contact pads 117 may comprisea layer of conductive material such as aluminum, but other materials,such as copper, titanium, or nickel may alternatively be used. The firstcontact pads 117 may be formed as an under-bump-metallurgy (UBM) layer.The first contact pads 117 may comprise a plurality of contact pads asshown in FIG. 1(a). Some of the contact pads may be located within thearea 112, while some other contact pads 117 may be located outside thearea 112. The first contact pads 117 may be formed using a depositionprocess, such as sputtering, to form a layer of material (not shown) andportions of the layer of material may then be removed through a suitableprocess (such as photolithographic masking and etching) to form thefirst contact pads 117. However, any other suitable process, such asforming an opening, depositing the material for the first contact pads117, and then planarizing the material, may be utilized to form thefirst contact pads 117. The first contact pads 117 may be formed to havea thickness of between about 0.5 μm and about 4 μm, such as about 1.45μm. The first contact pads 117 may comprise multiple sub-layers, notshown.

The second metal layer 119 may be formed over the second side of thesubstrate 101 to interconnect the second side of the substrate 101 toexternal contacts. The second metal layer 119 may be a redistributionlayer (RDL). While illustrated in FIG. 1(a) as a single layer ofinterconnects, the second metal layer 119 may be formed of alternatinglayers of conductive material and may be formed through any suitableprocess (such as deposition, damascene, dual damascene, etc.). In anembodiment there may be one or more layers of metallization, but theprecise number of layers within the second metal layer 119 depends atleast in part upon the design of the interposer 100.

The second contact pads 121 may be formed over and in electrical contactwith the second metal layer 119 on the second side of the substrate 101.The second contact pads 121 may comprise aluminum, but other materials,such as copper, may alternatively be used. The second contact pads 121may be formed as an under-bump-metallurgy (UBM) layer. The secondcontact pads 121 may comprise a plurality of contact pads. The secondcontact pads 121 may be formed using a deposition process, such assputtering, to form a layer of material (not shown) and portions of thelayer of material may then be removed through a suitable process (suchas photolithographic masking and etching) to form the second contactpads 121. However, any other suitable process, such as forming anopening, depositing the material for the second contact pads 121, andthen planarizing the material, may be utilized to form the secondcontact pads 121. The second contact pads 121 may be formed to have athickness of between about 0.5 μm and about 4 μm, such as about 1.45 μm.

A dam 113 may be formed on the first metal layer 115, or on aninsulating or passivating layer formed on first metal layer 115. The dam113 surrounds an area 112, where the area 112 has a size that is biggerthan a size of a die so that the die may be placed within the area 112and packaged with the interposer 100, as illustrated in FIG. 1(b). Incross section view, two segments of the dam 113 are shown in FIG. 1(a).The overall dam together with the die placed in the area 112 may beillustrated in FIG. 2(a) or FIG. 2(b) in top view.

The dam 113 may comprise a conductive metal material such as aluminum,but other materials, such as copper, titanium, or nickel mayalternatively be used. The dam 113 may comprise a layer of metalmaterial and another layer of non-metal material, as shown in FIG. 1(b).When the dam 113 comprises a metal material, the dam 113 may be formedusing a deposition process, such as sputtering, to form a layer ofmaterial (not shown) and portions of the layer of material may then beremoved through a suitable process (such as photolithographic maskingand etching) to form the dam 113. The dam 113 may be formed at the sametime as the first contact pads 117. The dam 113 may be formed as part ofan under-bump-metallurgy (UBM) layer, just as the first contact pads117. It may be possible that the dam 113 is formed on a contact pad 117.In addition, any other suitable process, such as forming an opening,depositing the material for the dam 113, and then planarizing thematerial, may be utilized to form the dam 113. The positions and sizesof the dam 113 will be illustrated and discussed in FIG. 1(c). The dam113 surrounds a die that is packaged on the interposer and controls theshape of the edge of an underfill under the die.

The width, height, or diameter of the dam 113 may be about the same asthe connector such as a ball (or bump) diameter, or can be as much as1/10 of the size of the diameter of the connector such as the ball (orbump) diameter. For example, the dam 113 may be of a rectangle shapewith a width around 100 um-200 um, and a height in a range from about 20um to about 30 um. The height of the dam 113 may be of a similar size ofthe connector 129, which may be of a diameter size about 200 um. The dam113 may have a narrow, wide, or tapered shape. The dam 113 body may beof a substantially constant thickness. The dam 113 may be of othershapes such as a circle, an octagon, a rectangle, an elongated hexagonwith two trapezoids on opposite ends of the elongated hexagon, an oval,a diamond.

FIG. 1(b) illustrates a flip-chip package 200 where a die 131 ispackaged with the interposer 100 within the area 112 surrounded by thedam 113. In packaging the die 131, the die 131 is flipped so thatconnectors 125 contact a plurality of first contact pads 117 on thesubstrate 101 within the area 112. An underfill 123 is filled under thedie 131 and between the die 131 and the surface of the first metal layer115, in the area 112 surrounded by the dam 113. A dam 114 may be furtherformed of non-conductive material and placed on the dam 113. A pluralityof connectors 129 may be placed on the first contact pads 117 outsidethe area 112 to connect to other packages to further form a PoPstructure. A plurality of connectors 139 may be placed on the secondcontact pads 121 to connect, e.g., to a PCB.

The die 131 may be an integrated circuit chip formed from asemiconductor wafer. The die 131 may be any suitable integrated circuitdie for a particular application. For example, the die 131 may be amemory chip, such as a DRAM, SRAM, or NVRAM, or a logic circuit.

The connectors 125 may provide connections between the first contactpads 117 and the die 131. The connectors 125 may be contact bumps suchas micro-bumps or controlled collapse chip connection (C4) bumps and maycomprise a material such as tin, or other suitable materials, such assilver or copper. In an embodiment in which the connectors 125 are tinsolder bumps, the connectors 125 may be formed by initially forming alayer of tin through any suitable method such as evaporation,electroplating, printing, solder transfer, ball placement, etc., to apreferred thickness of about 100 μm. Once a layer of tin has been formedon the structure, a reflow may be performed in order to shape thematerial into the desired bump shape.

The underfill 123 between the die 131 and the surface of the first metallayer 115 strengthens the attachment of the die 131 to the interposer100 and helps to prevent the thermal stresses from breaking theconnections between the die 131 and the interposer 100. Generally, thematerial for the underfill 123, such as organic resin, is selected tocontrol the coefficient of thermal expansion and the shrinkage ofunderfill 123. Initially, liquid organic resin is applied that flowsinto the gap between the die 131 and the surface of the first metallayer 115, which subsequently cures to control the shrinkage that occursin underfill during curing.

As shown in FIG. 1(b), the distribution of underfill 123 is relativelyuniform under the die 131. However, the underfill 123 may flow over toother areas beyond the die area without control or support. The dam 113may prevent the overflowing of the underfill and confine the underfill123 to the area 112 defined by the dam 113. To form the underfill 123, ameasured amount of underfill is applied to flow under die 131 and fill avolume defined by the dam 113. In one embodiment, the volume of theunderfill 123 and the separation between the dam 113 and the die 131 areset according to the natural flow of the organic underfill 123 and thecure schedule during fabrication of device 200. In particular, thevolume of underfill 123 and the height, width of the dam 113, and theseparation between the dam 113 and the die 131 should provide totalfilling of the volume under die 131, and no or substantially nounderfill material 123 may flow out over the dam 113.

As shown in FIG. 1(b), a second dam 114 formed of non-conductivematerial may be placed on first dam 113 when the height of the first dam113 is not high enough to stop the overflow of the underfill 123. Thesecond dam 114 may be formed of a variety of non-conductive materialsincluding but not limited to a dispensed organic isolative material suchas benzotriazole (BT) or modified silicone, a thermo setting moldcompound such as epoxy creasol novolac (ECN) or a modified BT, or athermo plastic compound such as polyethyl sulfone (PES) polycarbonate orpolysulfone. A non-conductive dam material may be deposited on the firstdam 113 and form a desired shape. The second dam 114 may be formed usinga variety of techniques such as liquid dispense methods, injectiontransfer molding, and thermocompression transfer molding. The use ofdams formed of non-conductive material together with the metal materialsformed on the interposer can make the packaging more flexible, to adjustto different height and volume of the underfill material used in thepackaging process.

A plurality of connectors such as solder balls 129 and 139 may be formedon the first contact pads 117 and the second contact pads 121respectively. The connectors 129 may be used to connect to anotherpackage, such as a package 300 shown in FIG. 3. The connectors 139 maybe used to connect to a PCB. The number of connectors such as 129 and139 are only for illustrative purposes, and is not limiting. A connectormay be any connection devices such as a solder ball providing anelectronic connection. A plurality of connectors such as solder balls139 or 129 may be arranged in a ball grid array, form the terminals ofpackaged device and can be attached to a PCB or other circuitry.

FIG. 1(c) illustrates an embodiment of the relative positions and sizesof the dam 113, the location of the die 131, and the location ofconnectors 129. The layer 101 is the substrate as illustrated in FIG.1(a) and FIG. 1(b). The layer 102 may be a representation of a pluralityof layers such as metallization layers, contacts, passivation layers,and polymer layers which are not shown in FIG. 1(a). The first metallayer 115 is as shown in FIG. 1(a). The die 131 is connected to aconnector 125 such as a micro-bump, whose diameter may be around 50 um.The dam 113 may be of a rectangle shape with a width around 100 um, anda height in a range from about 15 um to about 30 um. The connector 129may be of a diameter size about 200 um. The distance between the dam 113and the connector 129 may be in a range from about 50 um to about 100um. The distance between the connector 125 to the connector 129 may bein a range from about 1050 um to about 1100 um. The distance between thedam 113 to the connector 125 may be in a range from about 850 um toabout 950 um. The measurements shown in FIG. 1(c) are only forillustration purposes and are not limiting. With the continuousreduction of feature sizes and package sizes, the measurements in otherembodiments may become smaller than the ones shown in FIG. 1(c).

FIGS. 2(a)-2(c) illustrate top views of embodiments of packages oninterposer 100 with the dam 113. FIG. 2(a) is a top view of the package200 shown in FIG. 1(b), where a die 131 is placed on top of theinterposer 100. The die 113 may be packaged with the interposer 100using a variety of technologies, such as a flip-chip wafer level packagetechnology as shown in FIG. 1(b), or using a wire bonding technique, orusing a flip-chip and bump-on-trace technique, which are not shown. Aplurality of connectors 129 is formed on the interposer 100.

As illustrated in FIG. 2(a), the dam 113 surrounds the die 131 in topview, where the dam 113 forms a continuous line surrounding the die 131.The two dam segments 113 shown in FIG. 1(a) is a cross-section view ofthe dam 113 shown in FIG. 2(a). Other form of dam embodiments may beformed. As illustrated in FIG. 2(b), a plurality of dam segments 113 maybe formed to surround the die 113, but the dam 113 is discontinuouscomprising a plurality of broken segments.

Furthermore, there may be multiple dams 113 formed to surround the die131, as shown in FIG. 2(c). There are two dams 1131 and 1132 surroundingthe die 131, where the dam 1131 and 1132 are continuous and encircle thedie 131. The width of the dams 1131 and 1132 may be the same as shown inpart (i) or different as shown in parts (ii) and part (iii). The twodams 1131 and 1132 shown in FIG. 2(c) are only for illustration and notlimiting. For example, one of the two dams or both of the two dams maycomprise discontinuous segments as shown in FIG. 2(b). In addition,there may be more than two dams formed on the interposer 100.

FIG. 3 illustrates an embodiment of a PoP structure formed by placing apackage 300 on the package 200, where the package 200 is the samepackage shown in FIG. 1(b). The package 300 and the package 200 may beelectrically coupled to form a PoP device. A set of connectors 129 maybe formed on the first contact pads 117 of the package 200 formed on theinterposer 100, and further connected to a set of contact pads 227 ofthe package 300. The connectors 129 may be PoP connectors in someembodiments.

The package 300 may have a substrate 301. A first metal layer 317 may beformed on one side of the substrate 301 and a second metal layer 315 maybe formed on another side of the substrate 301. A plurality ofconnectors such as contact pads 227 may be formed on the two metallayers 317 and 315. The contact pads 227 may be used to connect toanother package, such as package 200 at the bottom. A first IC die 308may be mounted on the second metal layer 315. A second IC 306 may bemounted on the first IC 308, separated by an attachment material such asa thermally conductive adhesive, to provide improved thermalconductivity between the dies. Both the first IC 308 and the second IC306 may be connected to contact pads 227 on the second metal layer 315using the side electrical interconnections 310. An encapsulant or moldcompound 312 may cover the components such as ICs 306 and 308, the sideelectrical interconnections 310, the contact pads 227, and the secondmetal layer 315. Through vias (TVs) (not shown) may be used to provideelectrical connections between the die 308 and other circuits throughthe substrate 301.

In an embodiment, the substrate 301 may be any suitable substrate, suchas a silicon substrate, a high-density interconnect, an organicsubstrate, a ceramic substrate, a dielectric substrate, a laminatesubstrate, or the like. The dies 308 and 306 may be memory chips, suchas DRAM, SRAM, or NVRAM, and/or or logic chips for a particularapplication. There may be a plurality of dies mounted on top of eachother or on the side. The first metal layer 317 and the second metallayer 315 may be redistribution lines (RDLs). The side electricalinterconnections 310 may be bond wires. The connectors 227 may comprise,for example, contact pads, lead free solder, eutectic lead, conductivepillars, combinations thereof, and/or the like.

The encapsulant or mold compound 312 may be formed over the componentsto protect the components from the environment and externalcontaminants. The encapsulant 312 may be formed from a number ofmaterials, such as an elastomer or a rigid resin (thermoset epoxy,silicone and polyurethane), and is used to encapsulate and protect theinternal stacking components from shock and vibration.

It should be understood that the above description provides a generaldescription of embodiments and that embodiments may include numerousother features. For example, embodiments may include under bumpmetallization layers, passivation layers, molding compounds, additionaldies and/or substrates, and the like. Additionally, the structure,placement, and positioning of the die 306 and the die 308 are providedfor illustrative purposes only, and accordingly, other embodiments mayutilize different structures, placements, and positions.

Thereafter, other normal processes may be followed after the completionof the formation of the PoP structure. For example, the PoP structuremay be attached to a printed circuit board (PCB), a high-densityinterconnect, a silicon substrate, an organic substrate, a ceramicsubstrate, a dielectric substrate, a laminate substrate, anothersemiconductor package, or the like, through the connectors 139 at thepackage 200.

One embodiment includes a method of forming a device. The methodincludes forming a metal layer above a substrate, forming a firstcontact pad and a second contact pad above the metal layer, and forminga first dam above the metal layer. The first dam includes a first layerof conductive material and a second layer of non-conductive material.The first dam surrounds an area having the first contact pad within thearea. The the second contact pad is outside the area.

Another embodiment includes a method which includes forming aredistribution layer over a substrate. A first contact pad and a secondcontact pad are prepared above the redistribution layer. A conductivefirst dam layer is deposited above the redistribution layer. The firstdam layer surrounds the first contact pad. The second contact pad isoutside the first dam layer surround. A non-conductive second dam layeris deposited on the first dam layer. A first die is coupled to the firstcontact pad. An underfill is inserted under the first die. The underfillcontacts inner sides of the first dam layer and the second dam layer,where the inner sides face the first die.

Another embodiment includes a method of forming a semiconductor die thatincludes preparing a substrate and forming a metal layer over thesubstrate. A first die area is deposited over the metal layer. A seconddie area is deposited over the metal layer. A first dam is depositedaround the first die area while depositing the first die area. The firstdam is not deposited around the second die area. The first dam comprisesconductive material. A second dam can be deposited on the first dam. Thesecond dam comprises non-conductive material.

Although embodiments of the present disclosure and their advantages havebeen described in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the disclosure as defined by the appendedclaims. For example, it will be readily understood by those skilled inthe art that many of the features, functions, processes, and materialsdescribed herein may be varied while remaining within the scope of thepresent disclosure. Moreover, the scope of the present application isnot intended to be limited to the particular embodiments of the process,machine, manufacture, composition of matter, means, methods and stepsdescribed in the specification. As one of ordinary skill in the art willreadily appreciate from the disclosure of the present disclosure,processes, machines, manufacture, compositions of matter, means,methods, or steps, presently existing or later to be developed, thatperform substantially the same function or achieve substantially thesame result as the corresponding embodiments described herein may beutilized according to the present disclosure. Accordingly, the appendedclaims are intended to include within their scope such processes,machines, manufacture, compositions of matter, means, methods, or steps.

What is claimed is:
 1. A method of forming a device, comprising: forminga metal layer above a substrate; forming a first contact pad and asecond contact pad above the metal layer; and forming a first dam abovethe metal layer, the first dam comprising a first layer of conductivematerial and a second layer of non-conductive material over a topsurface of the first layer of conductive material, wherein the first damsurrounds an area, the first contact pad being within the area, and thesecond contact pad being outside the area.
 2. The method of claim 1,wherein the conductive material is selected from a group consistingessentially of aluminum, copper, titanium, nickel, and combinationsthereof.
 3. The method of claim 1, wherein the first dam and the firstcontact pad are formed simultaneously.
 4. The method of claim 1, whereinthe non-conductive material is selected from a group consistingessentially of benzotriazole (BT), modified silicone, epoxy creasolnovolac (ECN), modified BT, polyethyl sulfone (PES) polycarbonate,polysulfone, and combinations thereof.
 5. The method of claim 1, furthercomprising: connecting a first die to the first contact pad above themetal layer within the area surrounded by the first dam.
 6. The methodof claim 5, further comprising: filling an underfill under the firstdie, above the metal layer, and contained within the area surrounded bythe first dam.
 7. The method of claim 1, wherein the first damcontinuously surrounds the area.
 8. The method of claim 1, wherein thefirst dam comprises discontinuous portions that are spaced around thearea.
 9. A method, comprising: forming a redistribution layer over asubstrate; preparing a first contact pad and a second contact pad abovethe redistribution layer; depositing a conductive first dam layer abovethe redistribution layer, the first dam layer surrounding the firstcontact pad, the second contact pad being outside the first dam layersurround; depositing a non-conductive second dam layer on the first damlayer, the second dam layer covering a top surface of the first damlayer; coupling a first die to the first contact pad; and inserting anunderfill under the first die, the underfill contacting inner sides ofthe first dam layer and the second dam layer, the inner sides facing thefirst die.
 10. The method of claim 9, wherein the first dam layercomprises a plurality of discontinuous segments.
 11. The method of claim9, wherein conductive material comprising the first dam layer isselected from a group consisting essentially of aluminum, copper,titanium, nickel, or a combination thereof.
 12. The method of claim 9,further comprising: attaching a connector to the second contact pad, theconnector having a first diameter, wherein a first dam comprises thefirst dam layer and the second dam layer, wherein the first dam is arectangular shape in plan view having a dam height in a range from abouta size of a the first diameter to about 1/10 of the size of the firstdiameter of the connector.
 13. The method of claim 9, wherein a firstdam comprises the first dam layer and the second dam layer, and thefirst dam is a shape of a circle, an octagon, a rectangle, an oval, or adiamond in plan view.
 14. The method of claim 9, wherein non-conductivematerial compising the second dam layer is selected from a groupconsisting essentially of benzotriazole (BT), modified silicone, epoxycreasol novolac (ECN), modified BT, polyethyl sulfone (PES)polycarbonate, polysulfone, or a combination thereof.
 15. The method ofclaim 9, further comprising: depositing a second dam surrounding a firstdam, the first dam comprising the first dam layer and the second damlayer.
 16. The method of claim 9, wherein the first dam layer and thefirst contact pad are formed simultaneously.
 17. A method, comprising:forming a first dam around a periphery of a die contact region of aninterposer, the first dam comprising a first layer of conductivematerial and a second layer of non-conductive material over a topsurface of the first layer of conductive material; simultaneously withforming the first dam, forming a first contact pad on the interposer,the first contact pad located outside the die contact region; mounting adie in the die contact region of the interposer; and depositing anunderfill material between the die and the die contact region, whereinthe underfill material spreads further than the die contact region inplan view and contacts the first dam, wherein the underfill material isprevented by the first dam from contacting the first contact pad, andwherein the first dam comprises a conductive material.
 18. The method ofclaim 17, wherein the first dam comprises a plurality of discontinuoussegments surrounding the die contact region.
 19. The method of claim 17,further comprising: forming a second dam comprising a second conductivematerial laterally spaced from the first dam further from the diecontact region.
 20. The method of claim 17, wherein the conductivematerial of the first dam layer is selected from a group consistingessentially of aluminum, copper, titanium, nickel, or a combinationthereof.